It is known that image forming apparatuses, such as electrophotographic printers, copiers, facsimiles, or multifunction apparatuses, may include detachable developing cartridges filled with developing powder or toner.
As a method of filling a developing cartridge with toner, one proposal has been made to fill the developing cartridge with toner with a density greater than an apparent loose density by inserting a nozzle of a toner filling machine into the inside of a casing of the developing cartridge and filling the developing cartridge with toner under compression from the toner filling machine.
However, when the developing cartridge is filled with the toner with the above method, not only the toner but also air is forced into the developing cartridge, and thus it is difficult to efficiently fill the developing cartridge with the toner in high density.